Fix overflow in disk_get_sector_size()

Oren Cohen · Oren Cohen · commit 37b54426569a · 2018-10-10T14:57:42.000+03:00
diff --git a/features/storage/filesystem/fat/FATFileSystem.cpp b/features/storage/filesystem/fat/FATFileSystem.cpp
@@ -166,9 +166,12 @@ void ff_memfree(void *p)
 }
 
 // Implementation of diskio functions (see ChaN/diskio.h)
-static WORD disk_get_sector_size(BYTE pdrv)
+static DWORD disk_get_sector_size(BYTE pdrv)
 {
-    WORD ssize = _ffs[pdrv]->get_erase_size();
+    bd_size_t sector_size = _ffs[pdrv]->get_erase_size();
+    MBED_ASSERT(sector_size <= DWORD(-1));
+
+    DWORD ssize = sector_size;
     if (ssize < 512) {
         ssize = 512;
     }
@@ -248,7 +251,7 @@ DRESULT disk_ioctl(BYTE pdrv, BYTE cmd, void *buff)
             if (_ffs[pdrv] == NULL) {
                 return RES_NOTRDY;
             } else {
-                *((WORD*)buff) = disk_get_sector_size(pdrv);
+                *((DWORD*)buff) = disk_get_sector_size(pdrv);
                 return RES_OK;
             }
         case GET_BLOCK_SIZE:

Original file line number	Diff line number	Diff line change
`@@ -166,9 +166,12 @@ void ff_memfree(void *p)`
`166`	`166`	`}`
`167`	`167`
`168`	`168`	`// Implementation of diskio functions (see ChaN/diskio.h)`
`169`		`-static WORD disk_get_sector_size(BYTE pdrv)`
	`169`	`+static DWORD disk_get_sector_size(BYTE pdrv)`
`170`	`170`	`{`
`171`		`- WORD ssize = _ffs[pdrv]->get_erase_size();`
	`171`	`+ bd_size_t sector_size = _ffs[pdrv]->get_erase_size();`
	`172`	`+ MBED_ASSERT(sector_size <= DWORD(-1));`
	`173`	`+`
	`174`	`+ DWORD ssize = sector_size;`
`172`	`175`	`if (ssize < 512) {`
`173`	`176`	`ssize = 512;`
`174`	`177`	`}`
`@@ -248,7 +251,7 @@ DRESULT disk_ioctl(BYTE pdrv, BYTE cmd, void *buff)`
`248`	`251`	`if (_ffs[pdrv] == NULL) {`
`249`	`252`	`return RES_NOTRDY;`
`250`	`253`	`} else {`
`251`		`- ((WORD)buff) = disk_get_sector_size(pdrv);`
	`254`	`+ ((DWORD)buff) = disk_get_sector_size(pdrv);`
`252`	`255`	`return RES_OK;`
`253`	`256`	`}`
`254`	`257`	`case GET_BLOCK_SIZE:`